In various medical fields and particularly in dentistry, it is desirable and often necessary to dispense materials into a prepared cavity or a crevice in relatively small but controlled increments or units of a product. This is particularly desired relative to the delivery of dental sealant materials, but also applies to certain other materials such as cements, adhesives, coating agents and the like. The present invention is directed to a syringe-like dispensing device capable of discharging relatively small metered quantities of material to a desired location for use and quickly repeating such discharges, if desired, until a sufficient amount has been applied where it is needed. The device of the present invention provides a means to deliver successive unit doses of cement, adhesives, pit and fissure sealants, filling materials and similar medical materials directly to the site in vivo.
Previous attempts have been made to discharge successive amounts of materials of various kinds by means of a syringe and certain syringes of a reasonably complex type have been developed and comprise the subject matter of the following U.S. Pats.:
U.S. Pat. No. 1,718,596--Smith, June 25, 1929 PA0 U.S. Pat. No. 141,583--Mapel et al., July 21, 1964 PA0 U.S. Pat. No. 3,517,668--Drickson, June 30, 1970
The syringes illustrated in said patents are of what is generally known as the pistol-grip type of syringe and include a lever movable relative to a handle and, in general, driving a piston rod having notches or teeth which are engaged by suitable advancing means actuated by the pivoted lever when moving toward and from said handle. In these devices, it also will be noted that a separate syringe having a movable piston therein is inserted within a compartment in the forward end of the barrels of the syringes. It also is to be noted that these prior devices lack precise control of the placement of the material in metered, pre-measured amounts, especially in small amounts.
A more simple type of multiple dosage syringe comprises the subject matter of prior U.S. Pat. No. 2,875,761 Helmer et al., dated Mar. 3, 1959. In this syringe, a plunger within the barrel of the syringe is actuated by an elongated member having a series of spaced notches therein which are capable of being engaged by a flexible stop member; the stop member riding along a smooth surface on the member until a subsequent notch is reached, at which time the flexible member drops into the notch and stops further feeding movement of the plunger.
The present invention, while not restricted thereto, primarily has been designed to support at the outer, delivery end thereof, a disposable, predosed ampule, syringe or cartridge such as that comprising the subject matter of prior U.S. Pat. No. 4,391,590 to Dougherty, patented July 5, 1983; but the invention is not particularly restricted to the employment of that specific cartridge or compule, details of such syringe being set forth below. Essentially, the invention dispenses material in metered, uniform doses or amounts which are clearly visible to the operator and such dispensing occurs by finger action of a control member which in no way is fatiguing due to minimum energy being required.